The present invention relates to a power generator that converts fluid energy such as wind power, water power, or heat into electrical energy and a power generation system including this power generator, and relates to an improvement in a power generation mechanism.
In general, this type of power generation apparatus is widely known as an apparatus that converts energy such as wind power, water power, or heat into electrical energy. Further, a mechanism that uses external energy to rotate a spinning rotor having the same power generation principle as that of a power generator and outputs an electric current produced in a coil by the rotating force is also widely known.
As a conventionally known power generator, for example, Patent Document 1 (Japanese Patent Application Laid-open No. 2008-086128) discloses a configuration that a magnet rotor having a plurality of magnetic poles arranged in a rotating direction is rotatably disposed to a housing, a coil frame is arranged on a housing inner wall to surround the rotor, and a winding wire is wound around this coil frame to configure a power generation unit. Furthermore, when the number of the winding wires is three or its multiple number, a three-phase alternating current can be obtained.
In a field type synchronous generator disclosed in Patent Document 1, since electromotive force is generated in a coil wound around a core, large magnetic field attracting force functions at the time of slow rotation or activation, and a large resistance (a cogging torque) acts. Therefore, effective power generation cannot be performed at a low wind velocity. Furthermore, it is also known that heat generated when producing electromotive force in a coil must be efficiently liberated.
Thus, for example, Patent Document 2 (Japanese Patent Application Laid-open No. 2002-320364) suggests a method for using a coreless coil to reduce the cogging torque. This publication suggests a power generation mechanism having a configuration that a magnet rotor has a plurality of magnetic poles arranged on a concentric circle with a rotary shaft at the center and a plurality of winding wires are arranged in parallel to the magnetic poles to form a coil layer.
When the magnet rotor is driven and rotated to produce electromotive force in a stator coil as described above, a change in energy such as wind power or water power becomes a problem. For example, in case of a wind generator system, an electric current having a predetermined voltage must be obtained even in a light wind state, and stable electric power must be obtained even in a high wind state. In conventional examples, when rotating one of a coil and a magnet forming a magnetic pole by using external energy to generate electromotive force in the coil, electromotive force characteristics of the coil and field characteristics of the magnet are set constant. Therefore, each of a lower limit value when the external energy that makes the power generation system to be operable is weak and an upper limit value when the same is strong is set to fall within a fixed range.
That is, it is known that in the synchronous generator, the cogging torque acts on a driving rotary shaft that rotates at a lower speed when rotating force of wind power or the like is small, so that stable electric power cannot be obtained. Further, likewise, when the rotating force of the wind power or the like is excessive, the rotary shaft rotates at an excessively high speed, and a frequency of electric power generated in the coil increases. When the electric power to be output is connected with an electric power system, reducing a rotating speed of an input source to be lower than a synchronous speed results in a decrease in frequency, and increasing the rotating speed to be higher than the synchronous speed results in a rise in frequency, thereby leading to a problem that the stable electric power cannot be obtained. Since this type of power generation system is installed in a place where an input in a predetermined range (predetermined strength) can be obtained, using the system for extensive purposes, especially installing the system as a small facility is difficult.
Thus, the present inventor has conceived an idea that a power generation enabling range can be extensively set by changing an inductance of a coil to a large or small value in accordance with an intensity of external energy.
It is a main object of the present invention to provide a power generator that can generate power having a predetermined voltage and a predetermined current even though external energy is slight or excessively strong when generating power by using water power or wind power. Furthermore, it is another object of the present invention to provide a system that can obtain power having a predetermined voltage and a predetermine current even through a wind-power generation system is in a slight or excessively strong wind state.